Which of the given formulae would be used to calculate the wavelength of an electron? Given its velocity(v), its mass (m) and constant h:
Correct answer: B. λ = h / mv
- A. v = f.λ
- B. λ = h / mv
- C. s = d/t
- D. p = λ x h
Explanation
The correct formula to calculate the wavelength of an electron is λ = h / mv, known as De Broglie's wave equation. This equation takes into account Planck's constant (h), the mass of the electron (m), and its velocity (v). Option B is correct because it correctly represents this calculation. Options A, C, and D are incorrect as they represent formulas for velocity, speed, and momentum, respectively, not wavelength.
This question appeared on the ETEA MDCAT 2013 paper, which you can sit online with every answer explained.
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The particle model treats light as photons with energy E equals hf and momentum related to wavelength. Questions involve the photoelectric effect, work function, threshold frequency, stopping potential and photon energy, while distinguishing particle behaviour from the wave description of interference and diffraction.
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